Made of the highest-quality hand-spun aluminum, Jo-Ral mutes are designed and tested to perform evenly in all registers. Jo-Ral mutes also feature neoprene-enhanced composite cork pads that provide extra durability. The result is a more pliable cork that grips well and doesn't dry out, become brittle, or break off, so it lasts longer while easily accommodating fine adjustments for a perfect fit.